Core Java (Beginner to Intermediate)

1. What are the main features of Java?
2. Explain JVM, JDK, and JRE.
3. What are the differences between == and .equals() in Java?
4. What is the difference between String, StringBuilder, and StringBuffer?
5. Explain the concept of OOP in Java (Encapsulation, Inheritance, Polymorphism, Abstraction).
6. What is a constructor in Java? Can we overload constructors?
7. What is the difference between method overloading and method overriding?
8. What is the difference between final, finally, and finalize()?
9. What are access modifiers in Java?
10. Explain static keyword and its usage.
11. Difference between throw and throws.
12. What is the this keyword in Java?
13. Explain wrapper classes and autoboxing/unboxing.
14. Difference between ArrayList and LinkedList.
15. What are HashMap, TreeMap, and LinkedHashMap differences?
16. Explain HashSet, LinkedHashSet, and TreeSet.